NEUROEPITHELIAL BODIES IN THE LUNG OF BASILISCUS-VITTATUS (REPTILIA, IGUANIDAE)

Background: Neuro-epithelial bodies (NEB) are corpuscles of currently equivocal function which are present in the lungs of vertebrates. Comp arative studies may help to elucidate their role. Methods: The NEB of Basiliscus vittatus (Reptilia, Iguanidae), a terrestrial lower vertebr ate able to dive, are for the first time examined by electron microsco py, immunocytochemistry, and for argyrophilia. Results: Most NEB conta in both immunoreactive calcitonin and serotonin but are not labelled w ith argyrophilia or immunocytochemistry against calcitonin gene-relate d peptide (CGRP), protein gene product 9.5 (PGP 9.5), or the Leu-7 epi tope (Leu-7). Therefore, in NEB of this species, the transcription of the calcitonin/CGRP gene exclusively favors the expression of calciton in and this is in contrast to the intrapulmonary small neurons. Also, a physiologic difference is expected in the metabolism of ubiquitin in NEB of B. vittatus vs. mammalian NEB and neurons. In addition, the NE B cells are always covered by at least a thin cytoplasmic extension of a neighbouring cell, indicating that luminal contact is not required. Stronger still, it appears that in some lower vertebrates contact to the airspace is avoided. Finally, we provide ultrastructural evidence for the basket-like innervation of NEB in some reptiles. This way of i nnervation possibly represents an evolutionarily different concept for interaction between NEB corpuscular cells and nerve fibers. Conclusio ns: Beyond the confirmation that morphology, content of biologically a ctive substances such as serotonin and calcitonin, and innervation are evolutionary well preserved features of NEB, the results reveal some intriguing features of B. vittatus NEB: strict separation of calcitoni n and CGRP, reduced need for the de-ubiquitinating enzyme PGP 9.5, lac k of luminal contact, and the basket-like innervation. The latter two properties possibly refer to a mechanoreceptor function of NEB in this species. (C) 1994 Wiley-Liss, Inc.